A flash memory device is a type of non-volatile memory, which maintains stored data even when its power is turned off. It has an advantage in that data processing speed in write, read and delete operations is comparatively high.
Accordingly, flash memory devices are widely used as data storage devices for the BIOS of a personal computer (PC), set-top boxes, printers and a network servers. Flash memory has frequently employed in cameras, cellular phones, and etc., in recent years.
In flash memory devices, a semiconductor device using a silicon-oxide-nitride-oxide-silicon (SONOS) structure is being used, and the SONOS-type memory device may have a variety of masks for forming patterns.